RFR: 8339576: Speed up raw bytecode processing in ClassFile API [v2]

[Chen Liang]

> Currently, raw bytecode access goes through multiple wrappers, include one from ClassFile API and another ByteBuffer for merged big endian value reads. We can merge the ByteBuffer =into the ClassFile API one (RawBytecodeHelper) for safer access.
> 
> RawBytecodeHelper is also restructured so we avoid allocating it on the heap. Large `rawNext` method is now also inlined into the smaller `next` method.
> 
> Current benchmark results show this significantly speeds up `jdk.classfile.Write` and some degree of speedup for simple lambda startup. The impact on general application workloads is minuscule, but this doesn't seem to bring any regression.
> 
> Pinging @wenshao and @cl4es for review.

Chen Liang has updated the pull request incrementally with one additional commit since the last revision:

  Avoid repeated field usage, eliminate bound checks

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20863/files
  - new: https://git.openjdk.org/jdk/pull/20863/files/59a95339..a8b9a820

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20863&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20863&range=00-01

  Stats: 12 lines in 1 file changed: 3 ins; 1 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/20863.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20863/head:pull/20863

PR: https://git.openjdk.org/jdk/pull/20863